1. Field of the Invention
The present invention relates generally to a seat slide device applicable to an automotive vehicle and, more particularly, relates to the seat slide device in which a lock mechanism which locks with a seat fixed onto the seat and slide device slid in a longitudinal direction of the vehicle is improved.
2. Description of the Related Art
Diversification of a seat layout is demanded in recent-year automotive vehicle seats. A seat slide device is installed not only on a front seat but also on a second seat or third seat of the vehicle. An installation of the seat slide device for the vehicle is as follows: an upper rail coupled to the seat is slidably assembled onto a lower rail fixed onto a floor of the vehicle and a lock mechanism is installed to modify and lock a slide position of the upper rail with respect to the lower rail.
The lock mechanism biases a lock arm pivotably attached onto the upper rail via a spring member and a lock pawl of the lock arm is fitted into each lock hole of the upper rail and the lower rail so that the upper rail is locked with respect to the lower rail.
An example comparative to the present invention will be described with reference to FIG. 6. As shown in FIG. 6, the lock arm is pivotably installed with a pivotal axle 12b as a center, pivotal axle 12b being along an elongate direction of upper rail 2. A height of lock hole 9 is needed to be larger than a vertical length of a portion overlapped between doughnut shaped orbits P indicating a pivotal orbit of the lock pawl to be fitted into a plurality of lock holes and a cross section of an upper wall portion 2b of upper rail 2. As shown in a left side of FIG. 6, in a case where pivotal axle 12b is disposed within an inside of upper wall portion 2b, upper wall portion 2b is separated in the leftward direction from a vertical plane passing pivotal axle 12b. Hence, the portion overlapped between doughnut shaped orbits P and the cross section of upper wall portion 2b becomes larger in the vertical direction so that the height of lock hole 9 is needed by H1. Whereas, as shown in the right side of FIG. 6, in a case where pivotal axle 12b is disposed approximately just above lock hole 9 so that upper wall portion 2b is approximately overlapped with pivotal axle 12b, the portion overlapped between doughnut shaped orbits P and the cross section of upper wall portion 2b becomes small in the vertical direction and the height of lock hole 9 is sufficiently needed only by H2. When a pivotal axle 12b is arranged at a position approximately just above lock hole 9, lock hole 9 formed on upper rail 2 can be reduced in the vertical direction. Since lock hole 9 is small, a strength of upper rail 2 against a bending becomes large. With these merits in mind, vehicular seat slide devices in each of which the pivotal axle of the lock arm is arranged approximately just above the lock hole have been proposed.
Various types of seat slide devices have been proposed as described above in each of which the pivotal axle of the lock arm is arranged just above the lock hole. Japanese Patent Application First Publication (tokkai) No. 2003-146119 published on May 21, 2003 (which corresponds to a U.S. Pat. No. 6,691,971), Japanese Patent Application First Publication No. 2004-122825 published on Apr. 22, 2004, and Japanese Patent Application First Publication (tokkai) No. 2004-231106 published on Aug. 19, 2004 exemplify previously proposed vehicular seat slide devices.
In a first one of the previously proposed vehicular seat slide devices disclosed in the Japanese Patent Application First Publication (tokkai) No. 2003-146119, a large window is formed on an upper wall portion of the upper rail and the whole lock arm is disposed at a position of the window. In a second one of the previously proposed vehicular seat slide device disclosed in the Japanese Patent Application First Publication No. 2004-122825, the large window is formed on an upper wall portion of the upper rail and the whole lock arm axially supported over the upper rail is inserted into the window. In a third one of the previously proposed vehicular seat slide devices disclosed in the Japanese Patent Application First Publication No. 2004-231106, a large opening is formed over a space between the upper wall portion of the upper rail to an upper side wall portion and the whole lock arm is arranged on the opening portion.